The present invention relates to a mechanical injection-pump governor with an electronically controlled torque control with a stepping motor that adjusts with its actuator a yielding full load stop that interacts with an adjustment member of an injection pump, with an end stop for the actuator serving as a reference point for adjustment of the actuator.
German Patent Application DE 32 43 349 A1 discloses a torque control with a stepping motor that via its actuator, actuates a lever which is pivotable about a pivot and the free end of which has the yielding full-load stop for the quantity-adjustment member of an injection pump designed as a distributor pump. A drag lever forming part of a governor linkage connection is placed with prestress against the full-load stop.
The actuator having the yielding full-load stop is bounded by an end stop arranged in the governor housing. This end stop serves as a reference point to secure a new torque-control setting before any setting of a new control value. The new control value is formed by an electronic control device from operating parameters of the internal-combustion engine and is output to the stepping motor as counted actuating steps. The actuator is driven to the end stop and is brought from there into the desired end position by the number of steps corresponding to the control value to be set.
An object of the present invention is to provide a torque control with which it is possible to carry out new torque-control adjustments in an improved manner, such that, in the event of a failure of torque control in an arbitrary position (i.e. the instantaneous position), emergency running is possible while avoiding impermissible exhaust gas emissions. This needs to be done without damage to the engine occurring and without the engine speed falling below a speed necessary for maintaining the operation of the internal-combustion engine.
This and other objects are attained by the present invention which provides a mechanical injection-pump governor with an electronically controlled torque control that operates on an adjustment member of an injection pump. The governor includes a yielding full-load stop interacting with the adjustment member of the injection pump, and a stepping motor having an actuator. This actuator is coupled to the yielding full-load stop, the stepping motor adjusting the yielding full-load stop via movement of the actuator along a full-load control path. The actuator has a projection on it. A first end stop serves as a reference point for the movement of the actuator. This first end stop is positioned a short distance beyond a maximum of the full-load control path of the actuator in a first moving direction of the actuator. A second end stop is positioned a short distance beyond a minimum of the full-load control path of the actuator in a second moving direction of the actuator. This second moving direction is opposite to the first moving direction. The first and second end stops interact with the projection to limit a torque-control range of the injection pump.
An advantage of the present invention is that in the event of a failure of torque control, the full-load characteristic of the engine is neither critically exceeded (with regard to increased exhaust gas emissions) nor critically fallen below. This ensures that proper engine operation is maintained. Another advantage, when there is trouble-free engine operation, is the provision of a very small distance between an end stop and the full-load control path nearest to the end stop at a certain speed value. This allows readjustments for small paths of the stepping motor without prejudicing the operating behavior of the internal-combustion engine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.